Dual cases leak from shifter

Rockbaron1

Rockbaron1

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Ive been having this problem for a while. My dual transfer cases seem to overflow and oil comes out the shifters and leaks down the side of the case soaking the under side of my truck in gear oil on long drives. We just got back from a 5500 mile camping, wheeling, overlanding trip and I am so sick of smelling gear oil. I have checked trans oil to make sure its not leaking into the cases and overflowing them, thats fine, no leaks between trans and t-case. I have the sheet metal baffles installed under the shifters with paper gaskets aviation sealer, the rubber boots are installed but they dont actually hold in the gear oil even when theyre hose clamped onto the shift housing. The only thing i can think of is maybe heat from my exhaust since i have a passenger side drop t-case and exhaust on the passenger side. The exhaust has heat shielding but maybe not enough? My t-case oil level is like 1.5 inches below the fill hole after 5500 miles and it was slightly overfilled when I left. Ive seen other people complain about this problem but never any real solutions, is it just a fact of lift with toyota dual cases?
 

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Only time I had this happen was an overfilled setup.
They do transfer fluids between themselves, are you sure everything was installed in the right places inside?

Longshot, incompatible lubricants?

Any history with it before?
Vent still present? ( seems there was one ? Maybe?)
 
Clb said:
Only time I had this happen was an overfilled setup.
They do transfer fluids between themselves, are you sure everything was installed in the right places inside?

Longshot, incompatible lubricants?

Any history with it before?
Vent still present? ( seems there was one ? Maybe?)
Click to expand...
I tore the whole dual case set up apart and reassembled in 2020 to try and solve this issue and no luck. I don’t remember the dual cases in my last truck having this problem but they always had lots of other leaks so who knows. This truck doesn’t seem to leak anywhere except out the top of the t-case. I used marlin crawlers assembly instructions to make sure I didn’t miss anything. I guess I’m going to try header wrap and more heat shielding where the exhaust passes by the tcase because I don’t know what else to do.
 
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I suppose the lube "could be boiling" yikes tho...
good luck
 
There is a baffle that goes in first under the shifter.

If the other comment says "boiling" that condition is almost always caused by water mixed with the gear oil.

Pull shifter, if missing baffle, find one. If baffle is there, change your gear oil.
 
Perhaps oil is getting forced into the front case causing it to be over full all the time.
 
Oddball said:
Perhaps oil is getting forced into the front case causing it to be over full all the time.
Click to expand...
There is a pump system. This pump system pushes oil forward into the gear reduction area. The adapter allows gear oil to continue to the front case. So you are correct, there is oil being forced. But it is low pressure. And naturally evens out.

There is 2 spacers on the output. Both look for speedo, but one is actually the fluid pump.
 
Are these both RF1A gear cases and how much fluid are you adding? 2 quarts in the rear and 1 in the reduction box is correct.
The transfer case does vent out the top on a stock shifter setup so if they're overfilled and hot, they will vent out the top.
 
total newb said:
Wtf do toyotas use for oil? Its been so long since i ****ed with them.
Might be to thick? Cant make it back fast enough through the gaps/drain size.
Click to expand...
Gear oil.

Is the baffle in there correctly? Flare goes down

Check in on the marlin crawler forum. It's active
 
I read all the way through. I see you have the baffles. You are wheeling, overlanding, blah blah. Are you going through deep water? You are probably just steaming out the fluid. Apparently you already know the shooters are the vents.
 
This used to happen to me after fordyce and early season Rubicon. After deep water trips, diffs and t case get drained and filled. You can do vents on the axle that fixes this. But to do the case you would have to buy sealed shifters (twin/triple stick) and run your vents
 
Maybe add a vent with a catch can? Path of least resistance and stuff.
 
I have the shifter baffles in and the rubber boots. I used fresh 75-90 gear oil from a new sealed container in the trans and t-case filled to the top of the fill hole. I left NJ for Montana and after a couple hours on the highway the smell of gear oil was pretty strong. When i got to Montana I went to a car wash and washed as much oil off the under carriage as possible. After a few days of driving around national parks, dirt roads, and some low range mountain trails the under carriage was soaked in gear oil again. When I got home the trans oil level is fine, the t-case is 1.5 inches below the fill hole. I can see where the oil has been dripping down from the shifter its definitely leaking from there. Ive also driven with center console and shifts boots off in the past and visually saw the oil coming up around the shifter. What I think I still need to confirm is that the output shaft seal is not also leaking. I put a new output shaft seal in the t-case before leaving for Montana, Maybe somethings wrong? Or maybe my output shaft bearing is worn allowing the seal to leak? I'm not sure, gonna try and mount the go-pro down there next time I drive it.
 
What color is the gear oil that's pumping out?

It's either air reated ( my fone won't spell that word today).
Or, milkshake.
Outside of that, I got nuthin
 
It doesnt look foamy to me. Just light brown color
 
Piggy backing off your post cause I feel your pain. Both my twin stick (chain drive) and crawl box were leaking around the shifter(s). The rear case had a loose shifter plate and the 4.7 case was missing the baffle plate :-(
1759897843422.png
 
I did some more investigating and I may have been mistaken. I think the shifters do leak a little but it appears I have a more significant leak from the output shaft even though it’s practically a brand new marlin hd output seal. I think the next step is to check the output shaft for runout, maybe it’s bent? I don’t think the rear bearing is bad, it has a slight amount of play but from what I’ve read that’s normal for a rf1a.
 
Sometimes it is from the splines and not the seal itself. When in replacing the seal. Put some silicone on the splines of the output shaft or on the flange before sliding it back on. Then tighten and stake the nut.
 
NOODLES said:
Sometimes it is from the splines and not the seal itself. When in replacing the seal. Put some silicone on the splines of the output shaft or on the flange before sliding it back on. Then tighten and stake the nut.
Click to expand...
Yes, I always clean gear oil off the splines and apply rtv before sliding the flange on.
 
I worked on the transfer case a little last weekend. In the first pic you can see how gear oil has been dripping down from the top. I also checked output shaft runout and bearing lash. Neither seemed excessive. The hd output seal seemed loose though, so I swapped it out for a new oem seal. Oil was definitely leaking past the seal and not through the splines on the flange.
 

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